The United States is now experiencing public health catastrophe on a scale not seen for more than a century. COVID-19 puts into stark relief the mutual obligations that reflect interdependence among participants in a common society. Drawing on the work of Amartya Sen concerning famine and related challenges, the author discusses the accompanying implications for social justice. Social justice in catastrophe requires strong social insurance structures and legal protections for the most vulnerable people, who would otherwise lack economic resources and political influence to protect their essential interests. Social justice also requires greater and more sustained attention to disaster preparedness and public health infrastructure—both of which are characteristically neglected, in part because the public health enterprise is identified with politically weak and often stigmatized populations.